According to Nintendo's medicore E3 Direct.... 3DS is still going strong and NX is likely coming out next year. The fact they even mentioned NX to the public, it's definitely a Wii U successor.Take my word: Zelda U, Metroid U, 3D Mario, New F-Zero*, real Animal Crossing U, Pokken Fighters, and third party partnerships** will all be ported or exclusive to NX.

*Miyamoto hinted at new F-Zero using new controller**Leaked shortly before E3.